Peru has declared a state of emergency in 10 regions as the cold snap continues. Above: a hut collapses under heavy snow. Photograph: AFP/Getty Images

Peru has declared a state of emergency in 10 regions as temperatures in the Andes this week plunged to their lowest levels in decades.

Tens of thousands of animals, including valuable alpacas, have died and crops have been ruined as heavy snowstorms continue to sweep the area. About 100,000 people living in vulnerable mountain communities, some as high as 15,000ft, have been affected.

Oxfam said Peru authorities suspected the extreme weather had been triggered by climate change. "The people at these high altitudes say that year after year the climate impacts are becoming stronger," said the charity's country co-ordinator, Frank Boeren. "The climate is more extreme and unpredictable, and there is more snow and hail and more frequent frozen spells in January and February." Some government aid had been delivered, he added.

Community observations are backed by government research. According to scientists in Lima and elsewhere, the rainy season is starting later in the mountains, with rainfall decreasing by about 12mm a year.

Although there have been waves of bitterly cold weather, overall temperatures have risen nearly 2C in the summer since 1965, while the range of temperatures over 24 hours has increased to nearly 27C, compared with 18C in 1980.

The changing climate and growing water scarcity has made many communities more vulnerable to disaster, as people move their herds to remote pastures at ever higher altitudes as the land near their homes wilt.

Boeren said: "Higher altitudes entail greater risk of being trapped in snowstorms and snow layers covering pastures during several days, which in turn results in animals' starvation. Meanwhile, the [declaration of emergency] is being repeated year after year.

"Regional and local governments [in Peru] are not making the effort to increase budgets for prevention and disaster-risk reduction. Oxfam and local partners have been working on climate-change adaptation to use less water, better insulate homes, and protect animals. An early warning system has also been set up in some communities."